The present invention relates to movable core guidewires, and more particularly relates to a guidewire having a distal closed end and a proximal open end and having a safety cover located thereon.
In medical procedures such as angiography, catheters must be positioned deep in the vascular system, and generally such catheters must reach difficult to access regions. In order to introduce such a catheter into the vascular system of a patient, a sharp cannula is inserted through the skin and into the vascular system, and then a spring guidewire is inserted through the cannula and advanced in the vascular system until its distal end reaches the location where the catheter tip is desired. The cannula is then removed from the patient's body and the catheter is inserted into the body by sliding it over the guidewire. The guidewire generally then is withdrawn, and the catheter is ready for use. Catheters are also used in non-vascular procedures such as urinary tract procedures, and are introduced as described above.
As used herein, the terms "catheter" and "guidewire" are meant to encompass all types of catheters and guidewires. Fog convenience, however, the specific examples discussed herein relate to procedures dealing with the vascular system. Nevertheless, the present invention is not limited to catheters and guidewires designed for the vascular system, and the benefits and advantages of the present invention apply equally to any medical procedure where a catheter must be introduced through the skin and reach a remote location in the human body.
The specific type of guidewire forming the present invention is the movable core guidewire. This type of guidewire generally is more flexible and steerable than the fixed core guidewire, and hence can be used in more difficult to reach locations of the body.
The core wire of the movable guidewire assembly provides a degree of strength, rigidity, and steerability such that the entire assembly can negotiate the vascular system. And it is known that the flexibility of the guidewire assembly can be altered by changing the flexibility of the core wire along the length thereof. Furthermore, with the movable core guidewire, the flexibility of the guidewire assembly at the tip can be altered by moving the core wire into and out of the guidewire distal end.
Structural integrity is another requisite for a successful guidewire. A broken guidewire, with the possibility of leaving debris in a patient's body, cannot be tolerated. A commonly employed precaution against leaving a broken guidewire tip in the vascular system of a patient, is the provision of a thin wire, termed a safety wire, inside the wound outer guidewire casing. The safety wire is customarily connected to both the proximal and distal ends of the guidewire to enable the removal of any broken fragments, should a break occur in the outer spring of the guidewire assembly. One disadvantage of the internal safety wire is that it occupies space in the interior of the guidewire. Furthermore, should there be a break in the guidewire, there would be jagged edges exposed at the position of the break, and hence there would be a risk of tearing tissue as the broken guidewire is retracted from the body.
Some guidewire assemblies having distal closed ends and proximal open ends use a safety wire of a circular cross section, such as that described in U.S. Pat. No. 4,548,206 to Osborne. Additionally, it recently has been proposed that the safety wire conform to the shape of the guidewire lumen on one of its surfaces; see commonly assigned U.S. patent application Ser. No. 061,146, filed June 12, 1986, disclosing a crescent-shaped safety wire. In these types of guidewire assemblies, the mere presence of the safety wire inside the lumen makes movement of the core wire more difficult.
Reference also is directed to a publication entitled "The SOS Open Ended Guide Wire From U.S.C.I. Application and Case Study", published by C. R. Bard, Inc., 1985, and a publication entitled "SOS Interventional Wire Guides", published by Cook Inc., 1986. In both of these publications, there are disclosed catheters utilizing movable core wires, wherein the catheters are open at both ends to perform injection and infusion functions. The catheters are coated on their exterior surfaces.
With these types of SOS interventional devices, there are disadvantages associated with guidewire usage. Specifically, with open ends, blood can enter the open tip of the catheter and form a clot which subsequently could be pushed out of the catheter into the vascular system by the core wire. In addition, once the catheter is used for infusion, a core wire can no longer be inserted into and manipulated in the lumen for performing guidewire functions. Furthermore, because the SOS devices are designed primarily for infusion, the core wires are relatively difficult to manipulate in the catheter structure.
The movable core closed end guidewire assembly of the present invention utilizes a safety cover that overcomes the above disadvantages of known closed end guidewire assemblies.